Eugene S. Takle
© 2001
Chisholm et al. (2001) give a brief overview of a proposed engineering solution to reducing atmospheric carbon dioxide and point out the serious environmental consequences. Ocean phytoplankton account for <1% of global photosynthetic biomass but fix (remove) almost half of carbon dioxide annually removed from the atmosphere. These tiny organisms are mostly eaten by other organisms, and most of the carbon they contain is returned to the atmosphere through respiration. However, some of this organic carbon sinks to the ocean floor and essentially is removed from the global carbon cycle. This process of downward irreversible flux of carbon is called ocean biological pumping.
It has been speculated that if this mechanism could be enhanced by fertilizing the phytoplankton with iron (the key nutrient limiting phytoplankton growth in polar oceans) that the pumping volume would be accelerated, thereby reducing the buildup of atmospheric CO2. A plausible explanation for low values of atmospheric CO2 during past periods (e.g., over the past 180,000 years) of high global aridity during which dust (including trace amounts of iron) are transported to the polar oceans is that the excess iron led to phytoplankton blooms that reduced atmospheric CO2.
Some experiments to evaluate the technical feasibility of this method ( Martin, et al, 2000, have demonstrated that it does in fact enhance phytoplankton populations, sometimes by 20 to 30 times.
References
Chisholm, S. W., P. G. Falkowski, J. J. Cullen, 2001: Dis-crediting ocean fertilization. Science, 294, 309-310. Ambiguous input redirect.
Martin, J. H. et al., 1994: Nature, 371, 123.
Coale, K. H., et al, 1996: Nature, 383, 495.
Boyd, P. W., et al. 2000: A mesoscale phytoplankton bloom in the polar Southern Ocean stimulated by iron fertilization. Nature, 407, 695.
Smetacek, V., U.S. JGOFS (Joint Global Ocean Flux Study) News 1, 11